I've finally started reading Object Oriented Perl by Damien Conway and am enjoying it tremendously. Taking some of his code, I use a closure to create a simple binary toggle (something similar was discussed in this node).

Pass the sub a positive integer, $x, and it returns an anonymous sub that automatically toggles between 1 and 0 every $x times it's accessed. The following snippet illustrates its use.

Update: Made a slight change so that $count could start at zero instead of negative one. I also liked extremely's use of the ternary ( w = x ? y : z ) operator to set $bit!

#!/usr/bin/perl -w
use strict;

my $cycle = initToggle( 3 );

for ( 1 .. 24 ) {
    print "$_\t" . &$cycle . "\n";
}

sub initToggle {
    my $limit = shift;
    my $count = 0;
    my $bit   = 0;
    unless ( $limit > 0 ) { die "initToggle() requires a positive argu
+ment\n" };

    return sub {
        $bit ^= 1 if $count++ % $limit == 0;
        return $bit;
    }
}

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In reply to Easy binary toggle at fixed intervals by Ovid

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